How Climate Change Could Impact Aviation Safety - Simple Flying

How Climate Change Could Impact Aviation Safety

Summary

- The Singapore Airlines incident highlights how climate change can lead to adverse weather conditions that affect airports and flights, impacting operations and safety margins.
- The flight crew's decision to hold out as long as possible in the hope of landing at the scheduled airport compromised safety margins, raising concerns about their approach to fuel management.
- Pilots may need to interpret operating procedures more conservatively in unpredictable flying environments caused by climate change, enabling earlier decisions to divert to alternate airports with higher safety margins.

In a recently released final incident report, the Singaporean Transport Safety Investigation Bureau (TSIB), part of the city country's Ministry of Transport, highlighted how climate change could introduce more adverse weather conditions at airports.

The TSIB reviewed the case of the Singapore Airlines flight SQ319 from London Heathrow Airport (LHR) to Singapore Changi Airport (SIN) in October 2022. During the flight, operated by a Boeing 777-300ER registered as 9V-SWH, it was forced to enter a holding pattern near the airport due to severe weather at the location.

However, running low on fuel, the flight crew diverted to a nearby airport: Batam Hang Nadim International Airport (BTH), Indonesia.

Yet the weather system, which affected SIN, also moved into the territory of BTH, resulting in the pilots being unable to land the Boeing 777-300ER at BTH on their first attempt.

Although they eventually managed to land at their diversion airport, the aircraft touched the ground with less fuel than the final reserve fuel (FRF) requirement, prompting the investigation by the TSIB.

Worsening weather at SIN

When the flight crew, consisting of two captains and a first officer, received the Terminal Aerodrome Forecast (TAF) for SIN, they did not consider taking up additional fuel. The decision was based on several factors, including that no extensive weather system would require deviation en route, and the weather at the destination airport would still be above “landing minimas,” according to the TSIB. Furthermore, the pilots knew that the aircraft had no mechanical issues, and typically, Air Traffic Control (ATC) would “shorten the flight track of the aircraft through European airspace.”

When the Triple Seven was in the Kuala Lumpur Flight Information Region (FIR), the Singapore Approach Control (SAC) personnel told the pilots that they would land on Runway 20R at SIN. SAC said:

“According to the flight crew, at that point, the flight management computer (FMC) indicated that their estimated fuel on landing was 7,000 kg [15,432.36 lbs], which was above the [FRF] requirement of 3,024 kg [6666.7 lbs].”

The report noted that the initial fuel load as the aircraft departed LHR was 106,164 kg (234,051.5 lbs). Four minutes later, after being told to line up for Runway 20R, SAC told the flight crew to begin holding over waypoint PASPU due to a tailwind on the runway, which was more than 10 knots (18.5 km/h) at 16:05 local time (UTC +8).

At 16:10 local time (UTC +8), the SAC provided an update to all traffic landing at SIN, stating that the new runway used for landings would be Runway 02L and also updating the subject flight crew. The TSIB pointed out that the weather continued to worsen at SIN, with ATC at the airport deciding “to hold off arrival traffic” at 16:27 local time (UTC +8).

Diverting to BTH

While SAC said it would provide a weather update, the Singapore Airlines flight crew had already begun considering potential diversion points, as they informed the local ATC that they could only perform a single hold due to low fuel.

The weather continued to deteriorate, with the Singapore Arrival Control (Arrival Control hereinafter) informing all arriving traffic that Runway 20L’s visibility had decreased to less than 500 meters (0.31 miles) at 16:33 local time (UTC +8). In light of this, the arrival controllers at SIN informed their Indonesian counterparts that the Singapore Airlines Boeing 777-300ER might divert to BTH.

At the time, the weather at the Indonesian airport was still “fine.”

As time passed, the pilots continued to emphasize to ATC that they could only perform a single holding pattern due to their fuel situation.

“[…] if they still could not have the clearance to commence approach to land at Changi Airport thereafter, they would need to divert to Batam Airport”.

As SIN was still unable to accommodate landing aircraft, the flight crew made the decision to divert to BTH at 16:44 local time (UTC +8). The TSIB noted that “this was the fourth flight to make the decision to divert to [an] alternate airport”. The pilots decided to land at BTH due to uncertainty that they could land at SIN and that landing at the former would still keep the flight in line with FRF requirements. Arrival Control positioned the B777-300ER to land on Runway 22 at the Indonesian airport.

However, just two minutes later, ATC informed the Singapore Airlines crew that their diversion approval was still pending. At the same time, Arrival Control transferred the aircraft to SAC, with the pilots now informing the controllers that “they were down to minimum fuel.”

At 16:53 local time (UTC +8), the pilots declared “Mayday Fuel”, as the fuel levels would go below the FRF minima upon landing at BHT.

Different opinions on safety margins

Following the Mayday declaration, and once the Singapore Airlines flight was handed over from SAC to Indonesia’s Tanjung Pinang Approach Control (TPAC), the Boeing 777-300ER was given landing priority. The flight crew attempted to use the pilot’s approach mode. While the 777’s autopilot flight director system successfully captured the localizer and glidescope modes, the captain’s attempts to engage the autopilot at 668 ft (203.6 m) above ground level (AGL) was met with a “NO AUTOLAND” message on the Primary Flight Display (PFD).

TSIB pointed out that this startled the pilot, with the captain subsequently noticing that the jet “was away from the centreline and glidepath of the runway”.

As such, the crew initiated a go-around at 132 ft (40.2 m) AGL. On their second attempt, the pilots had to go around due to a Ground Proximity Warning System (GPWS) triggered by an excessive sink rate. Finally, at 17:15 local time (UTC +8), the Singapore Airlines Boeing 777-300ER landed at BTH. The TSIB noted that the data from the Flight Data Recorder (FDR) was available, but the Cockpit Voice Recorder (CVR) data was overwritten.

Nevertheless, during their analysis, the Singaporean investigators stated that “the flight crew appeared to have preferred to land at the scheduled arrival airport, Changi Airport.”

As a result, holding out as long as possible, the flight crew traded off “reduced safety margins available” to them. The TSIB also noted that trading off those margins for when they eventually decide to divert could become problematic “should they need to perform more than one landing attempt due to unforeseen events.” The report quoted Singapore Airlines as saying…

“[…] the decision taken by the flight crew to stay in hold as much as possible in the hope that the scheduled arrival airport starts to accept arrivals again does not compromise safety margins”.

Climate change effects

The TSIB was adamant that since the local ATC told the Singapore Airlines crew that landing at SIN was not possible, “the flight crew could have made a decision [to divert to BTH earlier – ed. note] based on this information.” They also pointed out that three aircraft were given the same information, and they were “able to make a decision to divert earlier.” As mentioned earlier, when the B777 was still in a holding pattern, the weather at BTH was okay.

However, the TSIB’s report read that if the Singapore Airlines pilots were to divert earlier, it was “reasonable to believe” they would have landed at BTH in better weather. The investigators also noted that studies have shown that “one of the effects of climate change is more intense and more frequent storms in many regions exacerbated by extreme rainfall and flooding”.

“This may likely result in pilots operating into areas where the weather conditions exceed the limits to conduct a safe landing or results in loss of capacity of an airport that may impact the regional airspace system.”

Furthermore, climate change could make the flying environment “more unpredictable.” The TSIB continued that this incident “suggests that it may be prudent for pilots to interpret operating procedures in a more conservative manner” if ATC cannot provide definitive updates.

“This will allow pilots to make an earlier decision to divert, with higher safety margins, especially when weather conditions are favorable, to increase the chances of conducting a safe landing at the diversion aerodrome,” the TSIB concluded.

Since Singapore Airlines has taken several actions in response to the incident, including updates to its micro-learning module on inflight fuel management, diversions to alternate airports, and the declaration of low fuel state, the TSIB has not provided any safety recommendations.

No injuries were reported among the 280 people onboard. The Boeing 777-300ER was actively flying until September 30, 2023, with no flights operated since, according to flightradar24.com data.
Read the latest Boeing news here.

Extreme weather conditions affecting operations

However, the Singapore Airlines incident was just one of the few examples of extreme weather impacting operations within airports. Phoenix Sky Harbor International Airport (PHX) has had several extreme weather events when some aircraft were disallowed to take off due to the extreme temperatures.

In June 2017, American Airlines canceled and/or delayed more than 50 flights, specifically on the Mitsubishi CRJs from PHX, due to heat. Then, the airline’s spokesperson told CNBC that the hot weather was affecting flights, especially on the CRJs, whose license belonged to Bombardier at the time. American Airlines also said that the CRJ’s maximum operating temperature was 118°F (47.7°), according to NPR.

Aircraft performance is also affected by heat, with pilots having to work with reduced performance at airports experiencing extreme heat. This could result in fewer passengers being able to board the plane, as heat lowers the air's density, causing the wings and engines to perform less efficiently. Subsequently, such weather conditions result in lower maximum take-off weight (MTOW).

In one extreme case, Persian Gulf International Airport (PGU) in Iran experienced a heat index of 152°F (66.7°) in July 2023, according to The New York Times.

Sources: TSIB, flightradar24.com, CNBC, NPR, The New York Times

Singapore Airlines IATA/ICAO Code: SQ/SIA Airline Type: Full Service Carrier Hub(s): Singapore Changi Airport Year Founded: 1972 Alliance: Star Alliance CEO: Goh Choon Phong Country: Singapore